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fa-fw"></i></a></div></div></nav><div id="post-info"><h1 class="post-title">设计模式：Java枚举类与注解</h1><div id="post-meta"><div class="meta-firstline"><span class="post-meta-date"><i class="far fa-calendar-alt fa-fw post-meta-icon"></i><span class="post-meta-label">发表于</span><time class="post-meta-date-created" datetime="2019-09-30T14:45:23.000Z" title="发表于 2019-09-30 22:45:23">2019-09-30</time><span class="post-meta-separator">|</span><i class="fas fa-history fa-fw post-meta-icon"></i><span class="post-meta-label">更新于</span><time class="post-meta-date-updated" datetime="2021-03-24T11:53:23.154Z" title="更新于 2021-03-24 19:53:23">2021-03-24</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/Java/">Java</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-wordcount"><i class="far fa-file-word fa-fw post-meta-icon"></i><span class="post-meta-label">字数总计:</span><span class="word-count">973</span><span class="post-meta-separator">|</span><i class="far fa-clock fa-fw post-meta-icon"></i><span class="post-meta-label">阅读时长:</span><span>4分钟</span></span><span class="post-meta-separator">|</span><span class="post-meta-pv-cv" id="" data-flag-title="设计模式：Java枚举类与注解"><i class="far fa-eye fa-fw post-meta-icon"></i><span class="post-meta-label">阅读量:</span><span id="busuanzi_value_page_pv"></span></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><h1 id="枚举类替代整形常量"><a href="#枚举类替代整形常量" class="headerlink" title="枚举类替代整形常量"></a>枚举类替代整形常量</h1><p>枚举类的基本形式如下：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Apple</span>  </span>&#123; FUJI, PIPPIN, GRANNY_SMITH &#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Orange</span> </span>&#123; NAVEL, TEMPLE, BLOOD &#125;</span><br></pre></td></tr></table></figure></p>
<p><font color="#f07c82">enum</font>关键字指明一个类继承 <font color="#f07c82">abstract</font>Enum。</p>
<p>该类有两个重要的方法：</p>
<ol>
<li><p><font color="#f07c82">ordinal()</font>. 返回整形序列值（从0开始）</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Season</span></span>&#123;</span><br><span class="line">    SPRING, SUMMER, FALL, WINTER</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">System.out.println(Season.SPRING.ordinal())</span><br><span class="line"></span><br><span class="line"><span class="comment">// 打印 0</span></span><br></pre></td></tr></table></figure>
</li>
<li><p><font color="#f07c82">Enum()</font>. 只能被继承Enum的类调用的构造方法，枚举类中每个实例调用该方法实现赋值，每个实例的构造方法都是私有的。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">protected</span> <span class="title">Enum</span><span class="params">(String name, <span class="keyword">int</span> ordinal)</span> </span>&#123;</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.ordinal = ordinal;</span><br><span class="line">    &#125;</span><br></pre></td></tr></table></figure>
</li>
</ol>
<p><strong>枚举类的特征</strong><br><strong>1. 不能被继承其它类也不能被其他类继承，但可以实现接口，对枚举类内部实例进行组织。</strong><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">Info</span></span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span></span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Season</span> <span class="keyword">implements</span> <span class="title">Info</span></span>&#123;</span><br><span class="line">    SPRING(<span class="string">&quot;春天&quot;</span>), SUMMER(<span class="string">&quot;夏天&quot;</span>), FALL(<span class="string">&quot;秋天&quot;</span>), WINTER(<span class="string">&quot;冬天&quot;</span>);</span><br><span class="line">    <span class="comment">// 必须为private的构造器，因为枚举类本身是final的，其内部实例也是final，且在枚举类生成同时调用私有的构造器实现值的赋予</span></span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="function"><span class="keyword">private</span> <span class="title">Season</span><span class="params">()</span></span>&#123;&#125;</span><br><span class="line">    <span class="function"><span class="keyword">private</span> <span class="title">Season</span><span class="params">(String name)</span></span>&#123;</span><br><span class="line">        <span class="keyword">this</span> name = name;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 实现接口，每个实例都有该接口，可以返回对应的中文名称</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">(</span></span></span><br><span class="line"><span class="function"><span class="params">        return name;</span></span></span><br><span class="line"><span class="function"><span class="params">    )</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@test</span></span><br><span class="line">    System.out.println(Season.SPRING.getName());</span><br><span class="line">    <span class="comment">// 打印 春天</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>
<p><strong>2. 类中每个实例可以重写其中定义的抽象方法</strong></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Season</span> <span class="keyword">implements</span></span>&#123;</span><br><span class="line">    SPRING(<span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">(return <span class="string">&quot;春天&quot;</span>)</span>, </span></span><br><span class="line"><span class="function">    <span class="title">SUMMER</span><span class="params">(<span class="keyword">public</span> String getName(return <span class="string">&quot;夏天&quot;</span>)</span>), </span></span><br><span class="line"><span class="function">    <span class="title">FALL</span><span class="params">(<span class="keyword">public</span> String getName(return <span class="string">&quot;秋天&quot;</span>)</span>), </span></span><br><span class="line"><span class="function">    <span class="title">WINTER</span><span class="params">(<span class="keyword">public</span> String getName(return <span class="string">&quot;冬天&quot;</span>)</span>)</span>;</span><br><span class="line">    <span class="comment">// 必须为每个实例都重写抽象方法，否则报错</span></span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="function"><span class="keyword">private</span> <span class="title">Season</span><span class="params">()</span></span>&#123;&#125;</span><br><span class="line">    <span class="function"><span class="keyword">private</span> <span class="title">Season</span><span class="params">(String name)</span></span>&#123;</span><br><span class="line">        <span class="keyword">this</span> name = name;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 实现接口，每个实例都有该接口，可以返回对应的中文名称</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">abstract</span> String <span class="title">getName</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@test</span></span><br><span class="line">    System.out.println(Season.SPRING.getName());</span><br><span class="line">    <span class="comment">// 打印 春天</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><strong>3. 可利用枚举实现单例</strong><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> enmu Sigleton&#123;</span><br><span class="line">    SINGLETON;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">method</span><span class="params">()</span></span>&#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="string">&quot;method&quot;</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="meta">@test</span></span><br><span class="line">System.out.println(Singleton.SINGLETON.method())</span><br><span class="line"><span class="comment">// 打印 method</span></span><br></pre></td></tr></table></figure></p>
<p><strong>4. 调用values()方法遍历枚举类型中的每个实例</strong><br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">for</span>(Season season: Season.values)&#123;</span><br><span class="line">    System.out.println(season.getName());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>
<p><strong>嵌套枚举</strong></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// The strategy enum pattern</span></span><br><span class="line"><span class="class"><span class="keyword">enum</span> <span class="title">PayrollDay</span> </span>&#123;</span><br><span class="line">    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY,</span><br><span class="line">    SATURDAY(PayType.WEEKEND), SUNDAY(PayType.WEEKEND);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> PayType payType;</span><br><span class="line"></span><br><span class="line">    PayrollDay(PayType payType) &#123; <span class="keyword">this</span>.payType = payType; &#125;</span><br><span class="line">    PayrollDay() &#123; <span class="keyword">this</span>(PayType.WEEKDAY); &#125;  <span class="comment">// Default</span></span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">pay</span><span class="params">(<span class="keyword">int</span> minutesWorked, <span class="keyword">int</span> payRate)</span> </span>&#123;</span><br><span class="line">        <span class="keyword">return</span> payType.pay(minutesWorked, payRate);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// The strategy enum type</span></span><br><span class="line">    <span class="keyword">private</span> <span class="class"><span class="keyword">enum</span> <span class="title">PayType</span> </span>&#123;</span><br><span class="line">        WEEKDAY &#123;</span><br><span class="line">            <span class="function"><span class="keyword">int</span> <span class="title">overtimePay</span><span class="params">(<span class="keyword">int</span> minsWorked, <span class="keyword">int</span> payRate)</span> </span>&#123;</span><br><span class="line">                <span class="keyword">return</span> minsWorked &lt;= MINS_PER_SHIFT ? <span class="number">0</span> :</span><br><span class="line">                  (minsWorked - MINS_PER_SHIFT) * payRate / <span class="number">2</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;,</span><br><span class="line">        WEEKEND &#123;</span><br><span class="line">            <span class="function"><span class="keyword">int</span> <span class="title">overtimePay</span><span class="params">(<span class="keyword">int</span> minsWorked, <span class="keyword">int</span> payRate)</span> </span>&#123;</span><br><span class="line">                <span class="keyword">return</span> minsWorked * payRate / <span class="number">2</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;;</span><br><span class="line"></span><br><span class="line">        <span class="function"><span class="keyword">abstract</span> <span class="keyword">int</span> <span class="title">overtimePay</span><span class="params">(<span class="keyword">int</span> mins, <span class="keyword">int</span> payRate)</span></span>;</span><br><span class="line">        <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="keyword">int</span> MINS_PER_SHIFT = <span class="number">8</span> * <span class="number">60</span>;</span><br><span class="line"></span><br><span class="line">        <span class="function"><span class="keyword">int</span> <span class="title">pay</span><span class="params">(<span class="keyword">int</span> minsWorked, <span class="keyword">int</span> payRate)</span> </span>&#123;</span><br><span class="line">            <span class="keyword">int</span> basePay = minsWorked * payRate;</span><br><span class="line">            <span class="keyword">return</span> basePay + overtimePay(minsWorked, payRate);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h1 id="实例属性代替内置序数"><a href="#实例属性代替内置序数" class="headerlink" title="实例属性代替内置序数"></a>实例属性代替内置序数</h1><p>内置序数会随枚举内部类位置而改变，通过在内部类的实例属性实现标记与类的一一对应。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Ensemble</span> </span>&#123;</span><br><span class="line">    SOLO(<span class="number">1</span>), DUET(<span class="number">2</span>), TRIO(<span class="number">3</span>), QUARTET(<span class="number">4</span>), QUINTET(<span class="number">5</span>),</span><br><span class="line">    SEXTET(<span class="number">6</span>), SEPTET(<span class="number">7</span>), OCTET(<span class="number">8</span>), DOUBLE_QUARTET(<span class="number">8</span>),</span><br><span class="line">    NONET(<span class="number">9</span>), DECTET(<span class="number">10</span>), TRIPLE_QUARTET(<span class="number">12</span>);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> <span class="keyword">int</span> numberOfMusicians;</span><br><span class="line"></span><br><span class="line">    Ensemble(<span class="keyword">int</span> size) &#123; <span class="keyword">this</span>.numberOfMusicians = size; &#125;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">numberOfMusicians</span><span class="params">()</span> </span>&#123; <span class="keyword">return</span> numberOfMusicians; &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h1 id="按位属性替换为EnumSet"><a href="#按位属性替换为EnumSet" class="headerlink" title="按位属性替换为EnumSet"></a>按位属性替换为EnumSet</h1><p><strong>替代前:</strong></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Test</span></span>&#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="keyword">int</span> STYLE_BOLD          = <span class="number">1</span> &lt;&lt; <span class="number">0</span>;  <span class="comment">// 1</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="keyword">int</span> STYLE_ITALIC        = <span class="number">1</span> &lt;&lt; <span class="number">1</span>;  <span class="comment">// 2</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="keyword">int</span> STYLE_UNDERLINE     = <span class="number">1</span> &lt;&lt; <span class="number">2</span>;  <span class="comment">// 4</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="keyword">int</span> STYLE_STRIKETHROUGH = <span class="number">1</span> &lt;&lt; <span class="number">3</span>;  <span class="comment">// 8</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// Parameter is bitwise OR of zero or more STYLE_ constants</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">applyStyles</span><span class="params">(<span class="keyword">int</span> styles)</span> </span>&#123; ... &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><strong>修改后：</strong></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// EnumSet - a modern replacement for bit fields</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Text</span> </span>&#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="class"><span class="keyword">enum</span> <span class="title">Style</span> </span>&#123; BOLD, ITALIC, UNDERLINE, STRIKETHROUGH &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Any Set could be passed in, but EnumSet is clearly best</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">applyStyles</span><span class="params">(Set&lt;Style&gt; styles)</span> </span>&#123; ... &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// ----------------------------------------------------------------</span></span><br><span class="line">text.applyStyles(EnumSet.of(Style.BOLD, Style.ITALIC));</span><br><span class="line"></span><br></pre></td></tr></table></figure>
<h1 id="使用EnumMap"><a href="#使用EnumMap" class="headerlink" title="使用EnumMap"></a>使用EnumMap</h1><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Plant</span> </span>&#123;</span><br><span class="line">    <span class="class"><span class="keyword">enum</span> <span class="title">LifeCycle</span> </span>&#123; ANNUAL, PERENNIAL, BIENNIAL &#125;</span><br><span class="line">    <span class="keyword">final</span> String name;</span><br><span class="line">    <span class="keyword">final</span> LifeCycle lifeCycle;</span><br><span class="line"></span><br><span class="line">    Plant(String name, LifeCycle lifeCycle) &#123;</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.lifeCycle = lifeCycle;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span> <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// Using an EnumMap to associate data with an enum</span></span><br><span class="line">Map&lt;Plant.LifeCycle, Set&lt;Plant&gt;&gt;  plantsByLifeCycle =</span><br><span class="line">    <span class="keyword">new</span> EnumMap&lt;&gt;(Plant.LifeCycle.class);</span><br><span class="line"></span><br><span class="line"><span class="keyword">for</span> (Plant.LifeCycle lc : Plant.LifeCycle.values())</span><br><span class="line">    plantsByLifeCycle.put(lc, <span class="keyword">new</span> HashSet&lt;&gt;());</span><br><span class="line"></span><br><span class="line"><span class="keyword">for</span> (Plant p : garden)</span><br><span class="line">    plantsByLifeCycle.get(p.lifeCycle).add(p);</span><br><span class="line"></span><br><span class="line">System.out.println(plantsByLifeCycle);</span><br><span class="line"></span><br></pre></td></tr></table></figure></article><div class="post-copyright"><div class="post-copyright__author"><span class="post-copyright-meta">文章作者: </span><span class="post-copyright-info"><a href="mailto:undefined">孙云增</a></span></div><div class="post-copyright__type"><span class="post-copyright-meta">文章链接: </span><span class="post-copyright-info"><a href="https://sunyunzeng.com/%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F%EF%BC%9AJava%E6%9E%9A%E4%B8%BE%E7%B1%BB%E4%B8%8E%E6%B3%A8%E8%A7%A3/">https://sunyunzeng.com/%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F%EF%BC%9AJava%E6%9E%9A%E4%B8%BE%E7%B1%BB%E4%B8%8E%E6%B3%A8%E8%A7%A3/</a></span></div><div class="post-copyright__notice"><span class="post-copyright-meta">版权声明: </span><span class="post-copyright-info">本博客所有文章除特别声明外，均采用 <a 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